The invention concerns the fluoroscopy and, in particular, the treatment of a sequence of fluoroscopic images of a body, particularly of a human body.
The invention further applies, in particular, to cardiac fluoroscopy.
By comparison with radiography in acquisition mode, where the X-ray doses are greater, in order to obtain better quality registered images for diagnostic purposes, fluoroscopy is carried out with weaker X-ray doses and is, in particular, used in the surgical field, for example, to position coronary endoprostheses (“stent” in English) by means of catheters.
In fluoroscopy the movement of the objects of interest, like, for example, coronary endoprostheses, as well as, notably, in cardiac fluoroscopy, the background movement, associated linked, for example, with the patient's respiration, as well as with the movements of the table on which the patient is placed, produce disturbances in the images, to which is added noise, particularly of electrical origin. That noise is all the more disturbing, the longer the fluoroscopic examination lasts, typically about 45 minutes, in order to position an intravascular prosthesis correctly, and produces, consequently, a visual inconvenience for the physician.
In the presence of immobile images, the noise could easily be eliminated by simple temporal filtering. However, in fluoroscopy mobile images are present, which are translated, if a filtering of images (for example, a filtering by temporal means) is simply carried out, by a blurred movement or else a loss of contrast of the mobile objects (depending on the size of the objects). In other words, there is then no difference between the arrival and departure of an object of interest and a noise peak.
At present, the standard algorithms of image processing in fluoroscopy resort to a criterion of distinction between a variation due to noise and a variation due to movement. The filtering treatment is then stopped or diminished in the presence of a movement. However, the cessation of filtering produces a recurrence of the noise, which is translated on the images by noise trails behind the mobile objects.